THE HISTORY OF THE MODERNMEDITERRANEAN BASIN

MESOZOIC TO HOLOCENE

LOCATION OF PLACES DISCUSSED IN MANY MED “RECONSTRUCTION” PAPERS

Many of the Mesozoic carbonates we see in theMediterranean (as seen during our Sicilian visit)developed on newly rifted continental margins that formed during the Mesozoic on the margins of both the northern and southern Tethyan seaway (see diagrams to follow for position of plates and their margins).

180 MaToarsian-Aalenian

MESOZOIC EVOLUTION OF THE TETHYS

SICILY

CLEAR CENTRAL ATLANTIC OPENING BEGINS

SICILY

NOTE SUSTAINED OPENING OF THE CENTRAL ATLANTIC

INCIPIENT N. ATLANTIC RIFTING

PYRENEAN SEA FLOOR

NEW ALBORAN-BALEARIC OCEAN FLOOR

SICILY

NORTH ATLANTIC SPREADING

PYRENEAN CLOSURE

SOUTH ATLANTIC OPENING

SICILY

There were numerous depositional facies groupings developed upon these rifted zones (as seen at Rocca Busambra- on our last day in the field), commonly formed within diverse environments (see rift figures to follow).They were deposited within different areas and ALSO during DIFFERENT time periods during this rifting phase. For example the Sicani or Imerase chains of Sicily, discussed in the literature (studies by Catalano, and Lentini, for example) are representative of different parts of these rifted zones. Each chain (later tectonized)is different because the sediments formed on different parts of the rifted margin or at different times.

Fig. 10a. A panoramic view of the southern slope of Piano Pilato (Rocca Busandra) show- ing stepped faults and paleoscarps; INI= lower Liassic peritidal limestones; J= Jurassic deposits; b= Geological map of the area (Basilone, 2008).

(Basilone, 2008).

The following figures demonstrate how a rifted margin develops and why segments of it receivesuch different sediments.

VERY SIMPLFIED DIAGRAM ILLUSTRATING THEFIRST STAGE IN DEVELOPMENT OF A RIFT ZONE-MAGMA IS STARTING TO RISE ALONG A LINEARRIFT ZONE WITHIN AN EXISTING CONTINENTALZONE (crust above initial rift is heated, uplifted, and stretched).

DIKES, VOLCANOES

INITIAL HEATING

DIAGRAM ILLUSTRATING MORE REALISTIC DEVELOPMENT OF FIRST STAGES OF RIFTING WITH

TILTING OF RIFTED BLOCKS

OPENING OF A RIFT ZONE WITH DEVELOPMENTOF NEW OCEAN FLOOR- MAY REMAIN CONTINENTAL (WITH OR WITHOUT INFILLING LAKES) OR MAY BECOME FLOODED WITH MARINE WATER.SUBSIDENCE OF CONTINENTAL MARGINS IS RAPID,DUE TO THINNED, STRETCHED CRUST+ COOLING. THINNING IS PARTLY DUE TO STRETCHING, BUT ALSO TO EROSION OF UPLIFTED (older) CRUSTAL SEGMENTS.

AMOUNT OF SUBSIDENCE AND TILTING OF BLOCKS IS UNEVEN, EVEN ALONG A SINGLEMARGINAL AREA.

ELONGATE LINEAR

SEAWAY

R

100 km

DIAGRAM OF A MESOZOIC TETHYAN PASSIVE MARGIN“R” IS A REEF STRUCTURE (weakly bedded to massive)

REEF MARGINAL AREAS (GREEN ARROW) USUALLY ARE WELL BEDDED. RED ARROW INDICATES AREAS OF

REEFAL TALUS AND SLUMPS

YELLOW ARROW INDICATES PELAGIC PLATFORMBERNOULLI, 1981

TRIASSIC REEF FACIES, GRUPPE SELLE, ITALIAN ‘DOLOMITES’

FORE-REEF DEBRIS]

REEF MARGIN DOWNSLOPE REWORKING

R

DEPOSITION AT THE BASE OF REEFSWITH ACCUMULATION IN GRABEN

OLISTOLITHS

GRUPPE SELLE, REEFAL OLISTOLITH,AT THE BASE OF THE MARGINAL SLOPE

REEFAL DEBRIS

ASSOCIATED PELAGIC PLATFORM

OFFSHORE PLATFORM WITH PELAGIC DEPOSITION

More confusingly they have been affected by later compressional tectonics that emplaced many separate deposits (even of different ages) together into a confused heap during the Cenozoic compression. These many segments are now shoved one upon the other in grouped chains that developed from related segments of the old Tethys rifted margins.

PLATE MOTION(why Sicily is such a mess)

Figure 3

Best for Spain Best for Sicily/Calabria

Best fit for E. Mediterranean

Position of Africa shown here presented with respect to Europe (for the past 175 Ma). Poles of rotation were worked out from magnetic position of Europe with respect to North America and then of Africa relative to North America. Rotation parameters were determined by comparing the finite difference solution of central and North Atlantic rotation parameters between the 2 areas. Then the motion changes of Africa with respect to Europe were directly related.

AFRICAN MOTION(early portion)

LATER AFRICAN MOTION(eastern Mediterranean pivoting

northward)

SUCCESSIVE PHASES OF MOTION OF THE NORTH AFRICAN COAST

SEPARATE SEGMENTS OF PLATES CONSIDEREDIN PLATE MOTION STUDY OF Dewey, Helman et al., 1989

Dewey, Helman et al. Were able to adjust the sense of rotation obtained from spreadingmotion based on detailed information obtained from each of the segments indicated above.

S

C

Dewey, Helman et al., 1989

OCEAN CRUST

MESOZOICCARBONATEPLATFORM

SENSEOF

MOTION

SENSEOF

MOTION

SICILY

ESTIMATED ANGLE OF ROTATION

OCEAN CRUST

Dewey, Helman et al., 1989

OCEAN CRUST

SICILY

S

C

OCEAN CRUST

ESTIMATED ANGLE OF ROTATIONESTIMATED ANGLE OF ROTATION

Dewey, Helman et al., 1989

OCEAN CRUST

SICILY

S

C

OCEAN CRUST

TORTONIAN

Dewey, Helman et al., 1989

OCEAN CRUST

SICILY

CALABRIA

S

C

OCEAN CRUST

OCEAN CRUST

MESSINIAN

Dewey, Helman et al., 1989

OCEAN CRUST

OCEAN CRUSTS

C

PLIOCENE

S

C

Dewey, Helman et al., 1989

EVOLUTIONARY DIAGRAM SHOWING HOW THE STRUCTURES OBSERVED IN CALABRIA CAN BE RELATED TO THE SEQUENTIAL DEVELOPMENT OF THE APENNINE THRUST SYSTEM AND THE EXTENSIONIN THE TYRRHENIAN SEA FLOOR.

Because Sicily is made up of differentsegments with diverse history, each segment responded to compression with different behavior.Also compression in the central and eastern Mediterranean changed direction about 9 Ma ago(see Dewey, Helman et al. Fig 3, as marked) so that much of the last phases of tectonism are about 90° rotated from the earlier stages.

ROVERI et al., 2008

DURING THE MESSINIAN THE MEDITERRANEAN BECAME A RESTRICTEDWATER BODY BECAUSE INFLOW AND CIRCULATION OF MARINE WATER WAS LIMITED. SPORADIC PARTIAL DRAWDOWN PROBABLY TOOK PLACE.

DEVELOPMENT OF THE MESSINIAN BASINSIN SICLY AND WHAT HAPPENED TO THE MESSINIANMARGINAL SEDIMENTS DURING THEINCREASING SYNSEDIMENTARY TECTONISMAND BASINAL COMPRESSION

ROVERI et al., 2008

Cross-section A-A’ from previous figure

- note development of sub-basins (west to east) and the different styles and degrees of reworking of the gypsum formed at the margins.

REFERENCES

Bernoulli, D. 1981. Ancient continental margins of the Tethyan Ocean. In:Geology of Passive Continental Margins. In: AAPG Education Course Note Series #19. Geology of Passive ContinentalMargins. Chapter 5, 36 pp.

Basilone, L., 2008. Mesozoic tectono-sedimentary evolution of Rocca Busombra in western Sicily.Facies. V. 54:

Cavazza, W. Roure, F., & Ziegler, P.A. 2004. The Mediterranean Area and the Surrounding Regions:Active Processes, Remnants of Former Tethyan Oceans and Related Thrust Belts. In: Cavazza, W. et al. “The TRANSMED Atlas”:

Dewey, J. F., M. L. Helman, E. Turco, D. W. H. Hutton, and S. D. Knott .1989. Kinematics of thewestern Mediterranean. In: M. P. Coward, D. Dietrich and R. G. Park, eds.,Alpine Tectonics. Geological Society Special Publication 45. pp. 265-283

Roveri, M. , Lugli, S., Manzi, V., Schreiber, B.C. (2008) The Messinian Sicilian stratigraphy revisited: toward a new scenario for the Messinian salinity crisis. Terra Nova, 20, 1-6.

Stamfli, G.M. and Borel, G., 2004. The TRANSMED Transects in Space and Time: Constraintson the Paleotectonic Evolution of the Mediterranean Domain. In: Cavazza, W. et al. “The TRANSMED Atlas”: 53-80.